Semiclosed circuit type gas turbine plant having extraction controlled by circuit turbine governor



Dec. 2, 1952- R, STRUB 2,619,798

SEMICLOSED CIRCUIT TYPE GAS TURBINE PLANT HAVING EXTRACTION CONTROLLED BY CIRCUIT TURBINE GOVERNOR Filed Jan. 10, 1951 2 SHEETS-SHEET l FIG.I

INVENTOR Fem Sfra Dec. 2, 1952 R. STRUB SEMICLOSED CIRCUIT TYPE GAS TURBINE PLANT HAVING EXTRACTION CONTROLLED BY CIRCUIT TURBINE GOVERNOR 2 SHEETSSHEET 2 Filed Jan. 10, 1951 I INVENTOR Rene dzra 7 BY wk: um

ATTO R N EYS Patented Dec. 2, 1952 SEMICLOSED CIRCUIT TYPE GAS TUR- BINE PLANT HAVING EXTRACTION CON- TROLLED BY CIRCUIT TURBINE GOV- ERNOR Rene Strub, South Charleston, W. Va.

Continuation of application Serial No. 557,616, October 7, 1944. This application January 10, 1951, Serial No. 205,318. In Switzerland December 23, 1943 11 Claims. (Cl. Gil-39.18)

This application is a filed October 7, 1944, and a continuation of my copending application Serial No. 557,616, filed October 7, 1944, both now abandoned.

The invention relatesto a gas-turbine plant with the Working-medium performing a circuit from which apartial quantity is continuously extracted while in-its place a make-up quantity is supplied, at least one turbine being operatedby the quantity of medium flowing in the circuit and at least one other turbine by the working medium extracted from the circuit. It consists in that the output of the'extraction turbine is adjusted to difierent values by alteration of the speed of the circuit turbine.

The governor of the circuit turbine can adjust the extraction of working medium from the circuit and in particular the supply of working medium to the extraction turbine. The speed governing arrangement has in given cases a device for adjusting the normal speed of the circuit turbine. At least one compressor of the plant can be provided with a bypass pipe the flow regulating member of which is adjusted by the governor of the circuit turbine. The device for adjusting the normal speed of the circuit turbine may further adjust the fuel supply to the gas heater.

' The invention is explained in more detail below with the aid of the drawings, in which:

Fig. 1 illustrates schematically an embodiment of gas-turbine plant in accordance with the principles of thisinvention, and

Fig. 2 shows a hydraulic regulating device which can be employed for the gas-turbine plant shown in Fig. -11 Identical elements appearing in the two figures are denoted by the same numerals. The gas-turbine plant shown in Fig. 1 works with a circuit of a gaseous working medium, for instance air, .from which a partial quantity is continuously extracted and to which in return a' make-up quantity is continuously supplied. The working medium compressed by the low-pressure compressor I passes through the intermediate cooler 2 into the high-pressure compressor 3. After being brought to the highest pressure, it flows through the pipe 4 into the heat-exchanger 5,111 which it is preheated while flowing through the tubes 6. Through the pipe I the working medium flows further until it is divided up into two parts at the point 8.

The major part passes through the pipe 9 into the gas heater III andis brought up to its highest temperature while flowing over the heat-excontinuation-in-part of my copending application, Serial No. 557,615,

T operated by the partial quantity extracted from changer tubes H and is then supplied through the pipe I2 to the turbine I3. The working medium is expanded in the turbine, passes through the pipe I4 into the heat-exhanger 5v and here, while flowing over the heat-exchanger tubes 6. gives up part of its residual heat to the Working medium flowing through the tubes. The working medium passes further through the pipe I5 into the cooler I6, in which a further part of its residual heat is given up to a coolingmedium. Finally the working medium is again supplied through the pipe I! to the low-pressure compressor I, in which the circuit begins anew.

From the circuit of the working medium described a partial quantity is continually extracted at the-point 8 and is supplied as combustion air through the pipe I8 to support the combustion of fuel supplied by the burner IQ of the gas heater III. This combustion air, mixed with products of the combustion and in a greatly heated condition, flows through the heat-exchanger tubes II, in which a portion of its heat is given up to the working medium of the circuit flowing over the tubes. Afterwards the combustion gases pass through the pipe 20 into the turbine 2|.

In order to replace the quantity of working medium extracted from the circuit at the point 8, air from atmosphere is continuously supplied to the circuit by the compressor 22. This makeup quantity is introduced into the heat-exchanger 5 through the pipe 23 at a point 24 at which the working medium flowing over the heatexchanger tubes 6 is approximately at the same temperature and the same pressure as the makeup quantity.

The turbine I3 operated by the quantity of working medium flowing in the circuit drives the compressors I, 3 and 22, while the turbine 2| the circuit works as a useful output turbine, for instance driving a ships propeller 26 through a reduction gear 25. The turbine I3 and the com-'- pressors I, 3 and 22 are further coupled to 3-phase constant speed electric machine 21 which serves as a starting motor and man auxiliary dynamo or motor for equalizing surplus or lacking power.

The output of the extraction turbine 2| is adjusted to various values by the changing of the speed of the circuit turbine I3. In order to keep the speed of the circuit turbine I3 and of'the compressors I, 3 and 22 to a normal value set, the supply of working medium to the extraction turbine 2| is adjusted by the governor 28 of the circuit turbine. The governor 28 controls a flow regulating member 32 through the medium of an impulse transmitter 29, the impulse pipe 30 and the servomotor 3|. The flow regulating member is arranged in' a bypass pipe 33 which supplies working medium from the pipe 20, while bypass,- ing the first stage of the turbine 2|, to the following stages. The impulse transmitter 29 is designed as an isodrome device. The term isodrome is a common one outside the United States and is here used in the sense of tending to return to the same position. The use of the term in this sense is fully explained and a number of isodrome devices are illustrated in a work of German origin on governors, Die Reglung der'Kraft maschinne, by Fabritz, published under the au- Edwards at Ann Arbor, Michigan, 1944, and also in Regelung der Kraftmaschinne, by Max Tolle,

3rd Edition, pp. 818, 872 874. Further see U. S. Patent 1,748,506. After-each regulating process it reestablishes the normal speed in the circuit turbine |3, however great the load on the turbine may-be. A lasting-irregularity cannot present itself;

. The cross-section of 'flow of the regulating member 32 is reduced-as soon as the speed of the turbine 13 .falls below the normal value, but it is on the otherjhand increased as soon as the speed of theturbine |3 rises above the normal value. A diminution of the cross-section of flow of the regulating rmember 32 has the effect that-a smaller quantity of working medium is extracted from the circuit. In consequence, the quantity of working medium which flows through the combustion-chamber of the gas heater In decreases, so that the temperature in the combustion chamb'eroftheg'as heater becomes higher. Through the pipe 9 a larger quantity of working medium issuppiied .to the'gas heater and .then through the .pipe'liz toithe' turbine. i3.

. 'Theiturbine l3 thus receives an increasedquantitybf working'medium with greater heat content, so' ithat the'initial drop of speed of the circuit turbine belowthe normal, which started the regulating'pro'cess, is again'made up. 'Contrarily, an increase in the cross-section of flow of the regulatingme'mber32 causes the extraction from the circuit to become greater. .A smaller quantity of working *mediu'm with lower heat content is thensuppliedto the turbine l3, so thatthespeed of the "circuit turbine, which originally .rose, is again returned tothe required normal value.

The impulse transmitter 29 has a device 34 with the'aid of'which the normal value which ismaintained by the governor 28 can be adjusted by hand to correspond to the desired output of the whole plant. If a smaller normal value is adjusted for the speed of the circuit turbine, a smaller useful :output is obtained at the turbine 2|; with'ahigherr normal value, a-grea'ter useful output is. obtained.

The temporary influencing of the supply of working medium to the extraction turbine 2| during the regulating process has no disadvantageous-results forth'eiservice of the plant, as this secondary influence-ceases again when the new level of steady-running has been set. In particular when the .plant is employed for marine propulsion, the brief and slight chan e of speed resulting herefrom is cine-significance.

.--In the discharge .pipe 35, which leads from the supply pipe 20 of the extraction turbine 2| and directly intothe-discharge pipe 36, bypassing the turbine, a flow --regu.lating -mem-ber 31 is built.

The servomotor 38 is influenced by the governor 40 of the extraction turbine 2| by way of the impulse pipe 39. In the supply pipe 20 a further closing member 4| is placed, and this is also controlled by the governor '4 0 with "the aid of the servomotor 52 by way of the impulse pipe 43.

The servomotor 38 of the regulating member in the discharge pipe 35 may further be influenced by the governor 28 of the circuit turbine |3 by way of the impulse pipes 44 and 30 and the impulse transmitter 29.

The flow regulating member 31 in the discharge pipe 35 and the closing member 4| act in common as a rapid-closing device, in order immediately to interrupt the supply of working medium to the extraction turbine 2| when the limit of the admissible speed range is exceeded. A sudden interruption of the output given up is necessary if the speed of the turbine 2| should rise inadmissibly high, for instance: if the propeller should emerge from the water in ,high seas or if a variable pitchpropeller should not function, and on the other hand if for instance the power given up must be rapidly interrupted on account of danger.

If the limitof admissible speed is reached by the extraction turbine 2|, the governor 40 influences the servomotors 38 and42 simultaneously in such a way that the flow-regulating member 31 is opened and the closing member 4| is closed. The combustion gases of thegas-heater ||l then no longer flow to the turbine 2|, but through-the discharge pipe 35 direct into the dischargepipe 36. Through the influencing of the servomotor 38 by means of the governor 28 the cross-section freed by the flow regulating member 31 in case of rapid closing is set to correspond to the speed of 'the circuit turbine and; the load-on, the whole plant.

If rapid closing takes place at .low load, at which only a small quantity of working medium is supplied to the turbine 2 I, the cross-section of flow of the member 31 in the pipe 35 is smaller than at higher loads with a correspondingly greater quantity of working medium. The crosssection of flow set by the member 31 in case of rapidclosi-ng is so measured by the governor 28 that after rapid closing ,just as much working medium is passed through the discharge pipe 35 as immediately before rapid closing through. the extraction turbine 2|. In this way the end is attained thatrapid-closing can have no direct reactions on the circuit portions of the plant.

The flow regulating members :41 and -'5| and the throttling member:55 come into action illzSllC- cession When'the load isgvgreatly reduced and during no-load running, .in order to prevent-the compressors from pumping. With the flow regulating members single stages or a whole :compressor can be bypassed, so that the reduced quantity of working medium only flows through part of the compressor stages. In-this waypumpe ing isprevented. V r The compressor-22 has abypass pipe AS-which connects the suction pipe 46 to an intermediate stage. In this bypass pipe is arranged thefiow regulating member 41 which is controlled .by-a servomotor 48. The servomotor 48 is in communication throu h the impulse-pipe 49 withthe impulse-transmitter 29. V I

Between the coolers l6 and 2 a communication exists through the pipe 50, in which is built the flow regulating member 5|. The flow regulating member is influenced. with the aid of a servomotor "53, which-is.connectedthrough the-impulse pipes 54 and 49 to the impulse transmitting device 29. With the aid of this bypass pipe the low-pressure compressor I can be cut out, so that the working medium from the pipe passes direct through the cooler l6 and the intermediate cooler 2 into the high-pressure compressor 3.

In the suction pipe 46 of the compressor 22 is built the throttling member 55, which is infiuenced by means of the servomotor 56 from the impulse transmitter 29 through the pipes 49 and 51.

First the regulating member 41 of the compressor 22 is opened by means of the governor 28 through the impulse transmitter 29, and then the regulating member 5| of the low-pressure compressor l is opened. Finally a further decrease of the output is obtained by reducing the cross-sectional area of pipe 45 left free by throttling member 55 for the flow of working medium. The bypass member 41 allows part of the air delivered by the supercharging compressor 22 to flow back into the suction pipe, so that a lower pressure of the working medium in the circuit, corresponding to the lower load, is set. When the valve 5| is opened, the low-pressure compressor I is bypassed. The high-pressure compressor 3 will then in consequence of the lower pressure at which it receives its input, deliver the working medium flowing in the circuit at a lower pressure. When the suction pipe of the supercharging compressor 22 is throttled by the regulating member 55, the pressure of the working medium is finally reduced to such an extent that the plant can run without load at the normal speed.

The fuel supply to the gas heater must be altered to correspond to the output set by the speed. It must be possible for the process of adaptation to be accelerated by hand during the change of output. For this purpose there is in the fuel pipe 58 of the burner a regulating member 59 whose servomotor 60 can be influenced through the impulse pipes 30 and 64 by the hand setting device 34 of the impulse transmitter 29. Further, an influence is exerted by the temperature of the working medium in the pipe 12 by means of the temperature impulse transmitter 63 acting through the pipe 62, and finally an influence is exerted by the pressure in the combustion chamber of the gas heater I0 acting through the impulse pipe 6|.

The regulating device shown in Fig. 2 may be used for the gas-turbine plant shown in Fig. 1. The governor 28 is driven by the shaft 14 of the circuit turbine. It influences by way of an isodrome device the regulating member 32 in the bypass pipe 33 of the extraction turbine in such a way that the normal speed" set for the circuit turbine with the aid of the hand setting device 34 is maintained. The isodrome device is equipped with a yielding return system and consists of the servomotor 3| with the control valve 15, the return drag device 16 and the spring 11. The isodrome device can only come to rest when the lever 18 is in a position in which the spring 11 is without load and the control valve 15 is in its middle position and covers the control passages 19 and B0 of the servomotor 3|. The lever 18 can only come into this situation at one position of the-governor 28, namely that position which corresponds to the normal speed set by the lever 34'.

, If the speed of the circuit turbine rises above the normal speed set the governor collar 8! is 1ifted.u The fulcrum 82 of the lever 75 at first remains unmoved, but the valve 15 is drawn upwards. Pressure fluid can make its way from the pipe 83 through the control passage 89 into the cylinder space situated above the servomotor piston 84. The piston is pressed downwards, so that by means of the lever 85 and the yoke 86 the cross-section of flow of the regulating member 32 is enlarged. A larger quantity of working medium now flows to the extraction turbine and a smaller quantity to the circuit turbine. The initial speed deviation which started the regulating process is thus redressed.

A similar regulating process, but taking place in the opposite direction, sets in when the speed of the circuit turbine falls below the normal.

Then the cross-section of flow of the regulating member 32 is diminished by the governor 28 with the aid of the isodrome device. Less working medium flows to the extraction turbine, and. more to the circuit turbine, so that the speed again rises to the nomal value.

In order to avoid overregulation and the oscillation that might then be caused, the servomotor piston 84 brings the control valve 15 back towards its middle position during the regulating process by means of the drag coupling 16 and the lever 18. Meanwhile the spring H is stressed. In this way a force comes into action on the casing of the drag coupling 16 which also acts through the fluid contents of the cylinder spaces upon the drag piston 81. In the cylinder space below the drag piston there arises, in the case of a rise inspeed, a greater pressure than that in the cylinder space above the drag piston, so that the fluid contents below the piston pass through thethrottle passage 88 of the piston into the upper cylinder space.

The displacement of the piston 81 in the cylinder of the drag device 16 continues until the spring TI is without tension and the valve 15 remains in the middle position. The servomotor piston as is then no longer displaced and nofurther spring force is exerted on the drag coupling. This position of rest is only possible when the governor 28 is brought back exactly into the position corresponding to the normal speed set and thus the circuit turbine operating the governor has again reached the normal speed required.

By means of the lever 34 the required normal value for the speed of the circuit turbine and thus therequired useful output of the whole plant can be set. If the lever is moved in the minus direction of the double-headed arrow 89, the spring 11 isplaced under further tension. The lever 78 can then only come to rest in one position, in which the position of the governor collar 8i is correspondingly lower and the value of the normal speed is accordingly reduced. The useful output is then likewise diminished.

Contrarily, when the lever is moved in the plusdirection of the double-headed arrow 89, the normal speed is raised. The spring 11 is compressed, the position of rest of the governor collar 8| will thus lie higher and the normal speed of the circuit turbine to be maintained will be raised correspondingly. At the increased speed, an increased output is given off.

The regulating member 3? in the discharge pipe 35 branching off from the supply pipe 28 of the extraction turbine and the closing member M in the supply pipe 20 are influenced with the aid of the governor 40 operated by the shaft 90 of the extraction turbine if the speed of this turbine rises above the upper limit of the 'admissible speed range.

At admissible speed of the'extraction turbine the control valve 9I isina position in which pressure fluid from the pipe 62 can 'flow into the-pipe 93. This pressure fluid passes into the cylinder spaces above the pistons 94 and 95 ofthe servomotors 38 and 02, so that the regulating member 31 is closed .and the closing .member M is opened. The working 'medium flows through the pipe 20 without any hindrance .into the extraction turbine.

If the speed of the extraction turbine reaches the upper limiting value of the admissible speed range, the collar 9'! is lifted by means of the lever 96. The valve SI arrives in an upper position in which the connection between the pipes 92 and 93 is interrupted, while on the other hand communication is established between the pipes 92 and 98. The high-pressure fluid now flows into the cylinder spaces below the servomotor pistons 9-I and 95. The valve of the regulating member 31 is lifted until the servomotorpiston 94 comes up against the piston 99 and the closin member 4| is brought into the completely closed position.

The piston 99 is set through the yoke 85 and the isodrome device by the governor 28 of the circuit turbine and thus serves as an adjustable stop in such a way that the quantity of working medium led off through the discharge pipe 35 is just as great as the quantity of working medium flowing through the pipe 20 to the extraction turbine immediately before interruption. By this means the end is attained that when rapid closing of the extraction turbine takes place there are no direct reactions on the working of the circuit.

Rapid closing can also be brought about when the lever 34 is displaced into its end position in the minus direction of the double-headed arrow 89. Then the valve 9! is lifted by means of the lever I8 and the push rod 18A, so that pressure medium out of the pipe 92 can flow through the pipe 98 to the .servomotors 38 and 42. Finally the governor 28 of the circuit turbine can also, at too high speeds, bring the valve 9| .into the rapid closing positionby means of the lever 18. Such an action takes on special significance if trouble occurs inservice.

Independently of the isodrome device the ,gov-

ernor 28 controls the flow member 41 in the bypass pipe 45, the flow regulating member i in the bypass pipe 50 and the throttling member 55 in the suction pipe 46 in accordance with the speed of the circuit turbine, in order at low outputs to prevent any surging in the compressors. The lever I00 is turned about the fixed point IOI by the collar 8|. When the speed of thecircuit turbine rises, the throttling member I02 frees .a larger cross-section of flow, and when the speed falls, a smaller cross-section of flow. Fluid is supplied to the servomotors 48, 53 and 55 by the gearwheel pump I03, the pressure of this fluid rising higher in proportion as the cross-section freed by the throttling member I02 is smaller. The springs which load the pistons of the servomotors 48, 53 and 56 are so chosen relatively to each other that first the servomotor '48, then, when the control pressure rises, the servomotor 53, and finally, at the highest control pressure, the servomotor 58 came into action.

At a'certa-in speed of the circuit turbine the fluid pressure is so high that the piston of the servomotor 49 raises the valve of the regulating meinberl'l. As the speed;falls,lthe cross-section of'flow past the regulating member 41 becomes greater and greater. During .theialling of the speed and the corresponding .rise .of the control pressure in the servomotors, the piston or the servomotor 253 also begins .to lift thevalve 5i. whenxthetspeed is very :low, the pressure is .so high that :the piston of theservomotor '55 presses the member '55 towards the closed "position.

For accelerating the adaptation 'of the .fuel quantity to a changed load, the fuel supply .to theburner I9 can besetby handand further automatically by .the temperature of the heated working medium. The flow regulating member 59 arranged'in the fuel pipe 58 :has a valve Ill which can be set by means of the. hand lever '34 and additionally by the temperature impulse transmitter 63 :in the pipe I2 for the heated gas. The'possibilityof setting the quantity in this way is limited bymeans of the pressure impulseatransmitter I05 in such away thatzoscillations of the regulatingsystem are prevented.

The hand lever 34 acts through the linkageaI29 and the lever I30 on the lever I2I, which'adjusts the valve I04 of the regulating member 59 through the-spring122 and the rod I06. If the lever '34 is displaced in the plus-direction of the doubleheaded arrow 89, the valve I04 is drawn downwards in'the' plus-direction of the doubleheaded arrow IIS and the fuel'supplyincreased. A decrease intheitemperature during the rise-of output is then prevented.

.A movement of the lever 34 in the minus direction causes correspondingly a decrease inthe fuel supply. In this way a rise of the temperature during the decrease of .output is prevented.

The exact setting of the temperature to the normal after a change in the *output is performed automatically by the temperature impulse transmitter 63; The rod of the impulse transmitter 63 is sensitive to temperature and has a-coeflicient of thermal-expansion which is considerably greater than that of the tube I 2 surrounding it. The expansion dueto heat is transmitted through the levers I I1 and I I8, the servomotor II9. the link I20, the lever I2I and the spring I22 to the rod I06 of thei-fuel regulating member :59. A rise of temperature in the pipe I2 causes the controlvalve I23 in the servomotor I I9 to be lifted. As a result pressure fluid passes from the pipe I24 into the cylinder space situated above the servomotor piston I2.5,.so that the piston islowered. The cross-section of flow'of the fuel regulating member59 is diminishedthrough the lever 126, the link I20, the lever .iI2 'I, the spring I22 and the-rod I06. The risein temperature which initially caused theregulating process is neutralized 'by the decrease of the fuel quantity supplied.

The corresponding regulating aprocess sets in when the temperature falls below the normal. The fuel supply is then increased, "so that the temperature is again raised.

The servomotor 125 further influences the return drag device I21, by which the return lever H8 'is displaced and the spring 128 is loaded. By the displacement of the lever N8 :the control valve I23 is again returned towards its .middle position when aregulating processxbegins to take effect, so that the further deviation of theservomotorpiston I25 is damped or interrupted.

The Whole regulating device comes .to rest only in one definite position of the lever H 8, namely that in which the spring I28 is without load and the valve I23 is in its middle position. This mid- 'dle position corresponds to the normal temperature to be set by the thermostat 63.

For limiting deviations a pin I! is attached to the rod I06 of the valve I04, and this engages with the cam surfaces of the opening I98 in the plate I09. This plate is displaced in the directions of the double-headed arrow II3 by means of the rod III) and the lever III by the piston II 2 of the pressure impulse transmitter I95. An

increase in the pressure in the combustion chamber of the gas heater I0 gives rise to a displacement in the plus-direction of the double-headed arrow I I3, a decrease in the pressure in the combustion chamber to a displacement inthe minus direction. This displacement can be further influenced by hand by turning the lever -I I4 in the plus or minus direction of rotation of the double-headed arrow II5.

The cam surfaces of the opening I08 have such a form that at the various pressures prevailing in the combustion chamber of the gas heater II), or at the various loads for thefuel regulating member 59, a range of regulation is set-up in which no oscillations of the regulating system can arise. In case of large fuel quantities the range of regulation is greater than with small fuel quantities, as particularly with small fuel quantities the temperatureregulating device is in danger of working unsteadily.

,In a governing device a distinction must be made between the actual value and the desired value of the engine operating condition to be regulated, for example, output, or the speed, or the pressure, or the temperature, which may be necessary or desirable to govern.

In the case of the marine plant chosen as example in Fig. 1, the desired value of the speed of the ship is ordered from the bridge, and the corresponding desired value of the output of theturbine is then set by the engine room watch by hand lever 34. This hand lever 34 does not vary the output of turbine ZI directly, but infiuences it indirectly, in that, instead of the direct influencing, it sets (by means of II, 82, It) at the speed governor 28 driven by the turbine I3 another desired value of the speed of turbine I3, i. e. corresponding to the desired value of the output of turbine 2 I. Consequently the governor 28 has a device for varying the desired value of the speed of turbine I3. The speed governor 23, adjusted to, for instance, a higher desired value, then tends to suit the actual value of the speed of turbine I3 to the desired value, i. e. to increase it. Also this speed governor in its turn works indirectly, in that it does not influence the turbine I3 directly, but instead of this the turbine 2 I, and in fact in the first moment in an apparently opposite sense. In order to obtain the sought increasing of the actual value of the output of turbine 2 I, it first of all reduces the energy fed to turbine 2 I, so that its output in the first moments does not increase, but diminishes. But this initial reduction in the energy fed to turbine 2 I has the consequence that the pressures in the circuit begin to rise, and that therefore also the speed of turbine I3 and with it the speed of the compressors I, 3 and 22 rise, with in consequence an additional and more rapid rise in the pressure and thereby an additional and more rapid rise in the actual value of the speed of turbine I3, until this actual value finally reaches its desired value, and thereby also the actual value of the output of turbine 2I reaches its desired value. During the whole of this operation, the fuel feed to burner I9 is at the beginning only increased by an amount limited by the device fill-I09; but, with rising pressure in the circuit, this device--by means of the device IIilII2 influenced by the pressure in the circuit-gives an always increasing fuel feed corresponding to that pressure. In connection with this, the temperature is supervised by means of the thermostat 63 and associated apparatus.

In the marine plant chosen as exampl in Fig. l, the turbine 2| has only an overspeed safety governor 40, but not a speed regulating governor, for in a marine plant there is a certain propeller speed corresponding to each output. On the other hand, in plants which are driving not a propeller but, for instance, an electric generator, the order to vary the desired value of the output of turbine 2i is given not from the bridge but from the load itself. The turbine 2| or the electric generator driven by it must then be provided with a device responsivae to load, for example with a speed governor, or possibly with a device infiuencedby the electrical load, this varying the setting of the lever 34' automatically, instead of the engine room watch doing it.

If, contrary to what has been said above, the output of the turbine 2| is to be diminished, the operations are the same but in the contrary sense, at any rate as long as the position of the 1ever 34 is varied only by a slight amount, or only slowly by a greater amount in. the sense of reducing the desired value of the output. If on the other hand, the engine room watch finds it necessary to change the position of the'lever 34 quickly'by a very great amount in the sense of diminishing the desired value, the lever .18 then pushes the control piston BI up high, andthereby causes the same effect as if the safety governo 40 were to come into operation.

I-claim:

1. In a gas turbine plant of the type including a compressed air circuit which includes a circuit compressor, a gas heater having a combustion chamber and a heat exchanger for heating gas by heat exchange without intermixture with combustion products from said chamber, a conduit connecting an outlet of said compressor to an inlet of said exchanger, a circuit turbine, a conduit connecting an outlet of said exchanger to an inlet of said circuit turbine, and a conduit connecting an outlet of said circuit turbine to an inlet of said compressor; an extraction branch which includes a conduit connecting an outlet of said compressor to an inlet of said chamber, an extraction turbine, and a conduit connecting an outlet of said chamber to an inlet of said extraction turbine; and a make-up branch which includes means for delivering air to said circuit in a quantity to replenish air passing from said circuit to said chamber; the combination which comprises a speed governor driven by said circuit turbine and a flow control device influenced by said governor controlling the flow of combustion products from said chamber to reduce said flow in response to a drop in speed of said circuit turbine.

2. A combination according to claim 1 in which the flow control device regulates the volume of combustion products entering the extraction turbine.

3. A combination according to claim 1 in which the flow control device regulates the in-flow crosssection of the extraction turbine.

4. A combination according to claim 1 in which the circuit turbine drives the compressor and the extraction turbine drives the plant load.

5. A combination according to claim linwhich the: extraction turbine is. fitted with a bypass around at least one stage and the: flow control device regulates the flow throughsaidby-pa-ss;

6. A combination according toclaim 1 inwhich a safety'governor is driven by theiextraction-turbine, a cut-off valve in the conduit between the combustion chamber and said extraction turbine controlled by saidsafety governor, anoutle-t to atmosphere from said conduit between said chamberand said cut-off valve, an outlet valve regulating." the flow through said outlet controlled by; said safety governor, and an adjustable stop limiting the maximum opening to which said outlet valve can'lbe set controlled'by the circuit turbine governor.

7. In a' gas turbine plant of the type including a compressed air circuit which includes a circuit compressor, a gas heater having a combustion chamber and a heat exchanger'for heating gas by heat exchange without intermixture with combustion products from said chambena conduit connecting an outlet of said compressor to an inlet of said-exchanger, a circuit turbine. driving said circuit compressor, a conduit connecting an outlet of said exchanger to said inlet of said circuit turbine, and a conduit connecting an outlet of said circuit turbine to an inlet of said compressor; an extraction branch which includes a" conduit connecting an outlet of said circuit compressor to an inlet of said chamber, an extraction turbine not mechanically connectedto saidcircuit compressor, and a conduit connectinglan outlet of said chamber to an inlet of said extraction turbine; and'a make-up branch which includes av make-up compressor driven by said circuit turbine and a conduit connecting an outlet of said make-up compressor to a point in said circuit; the combination which comprises'a speed governor driven by said circuit turbine, means for varyingthe'sp'eed of said circuit turbinaan isodromedevice controlled by said speed governor and controlling said speed varying means, and means for setting the equilibrium value of saidisodrome device'to correspond to any desired circuit turbine speed;

8; A- combination according to claim 7 in which themeans for varying the speedof the circuit 12 turbine includemeans tor regulating: theflow from the combustion chamber."

9. A combination accordingfco cl-aim"8 in which the means for regulatingithe flow from" thecombustion chamber include means for controlling the quantity of combustion products supplied to the extraction turbine.

10. A combination according to claim 7 in which the meansfor varying the speed ofjthe circuit turbine include a by-pass around at least a portion of the stages of zit-least one of the compressors and a flow'control device'influenced by a circuit turbine governorrfor controlling; the flow through said by-pass.

11, A combination according to claim:- 7 in which the means for setting the-equilibrium value of the isodrome device include means for ad!- justing the quantity of fuel supplied to the com"- bustion chamber.

RENE. STRUB.

REFERENCES CITED The following references are of: record in the file of this patent:

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